The technique for determining percent stroke-length of the poppet of a prosthetic valve (Starr-Edwards) was developed in 1970 at the NIH. Other techniques for diagnosing ball variance have a low yield (approximately 25%) for detecting this possible fatal complication. The limiting factor in utilizing our technique is the ability to visualize the barium impregnated ball on cine. Fourteen patients have been studied and operated upon at the NIH for aortic ball variance since 1970. Twelve of these patients had other criteria of ball variance, but two patients were thought "normal" by existing criteria. The first patient required operation for a diseased mitral valve. The second patient was operated on for aortic ball variance determined by this technique and the poppet was found to be variant at the time of operation.